After being collected from a paddy field, the sample was put on 1% agar plate with a drop of distilled water and kept for four days.

The shape of this transparent organism riminds us of an arrowhead.

Commentary by Prof. Yuji Tsukii, Hosei UniversityFrom the way it moves, this organism may be a flagellate. Based on the fact that the hard body does not easily change its shape, and its triangular cross-section is slightly warped, this organism is most likely Petalomonas.

When this organism proceeds using the flagellum at the top, it shakes its posterior end slightly, as Petalomonas often does. But it is more than 50μm long, which is larger than the typical 30 mμlength of Petalomonas. There is a flagellate called Calycimonas that is larger than Petalomonas, but has a similar shape. However, the organism in this video is definitely not Calicimonas.

The triangular cross- section of the cell in this video suggests that the organism may be Petalomonas bicarinata, but the cell length of the latter is about 30μm long. Therefore it might be a larger mutant type of P. binacarinata or possibly another species.